Light emitting device and light emitting device package

ABSTRACT

Disclosed are a light emitting device and a light emitting device package. The light emitting device includes a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer. The active layer includes (T+1) barrier layers, T well layers between the (T+1) barrier layers, and a first dummy layer between N well layers adjacent to the second conductive semiconductor layer and N barrier layers adjacent to the N well layers, in which T&gt;N≧1.

The present application claims priority under 35 U.S.C. §119(a) ofKorean Patent Application No. 10-2012-0086010 filed on Aug. 6, 2012,which is hereby incorporated by reference in its entirety.

BACKGROUND

The embodiment relates to a light emitting device.

The embodiment relates to a light emitting device package.

A light emitting diode (LED) is a semiconductor light emitting diode toconvert current into light.

When comparing with conventional light sources such as a fluorescentlamp and an incandescent lamp, the light emitting device has advantagesin terms of low power consumption, a semi-permanent life span, a rapidresponse speed, safety, and an eco-friendly property. Accordingly,studies and researches to substitute the conventional light sources withsemiconductor light emitting devices have been carried out.

In addition, the light emitting devices are increasingly used accordingto the trend as light sources of a variety of lamps used in indoor andoutdoor places, light sources of lighting devices such as streetlamps,or light sources of display devices such as liquid crystal displays andelectronic display.

SUMMARY

The embodiment provides a light emitting device capable of enhancing acolor rendering index (CRI).

The embodiment provides a light emitting device capable of improvingoptical power.

The embodiment provides a light emitting device capable of loweringdriving voltage.

According to the embodiment, there is provided a light emitting deviceincluding a first conductive semiconductor layer, an active layer on thefirst conductive semiconductor layer, and a second conductivesemiconductor layer on the active layer. The active layer includes (T+1)barrier layers, T well layers between the (T+1) barrier layers, and adummy layer between N well layers adjacent to the second conductivesemiconductor layer and N barrier layers adjacent to the N well layers,in which T>N≧1.

According to the embodiment, there is provided a light emitting deviceincluding a substrate, a first conductive semiconductor layer on thesubstrate, an active layer on the first conductive semiconductor layer,and a second conductive semiconductor layer on the active layer. Theactive layer includes first to fourth barrier layers, and first to thirdwell layers between the first to fourth barrier layers. The firstbarrier layer contacts the first conductive semiconductor layer, thefourth barrier layer contacts the second conductive semiconductor layer,and the third and fourth barrier layers have thicknesses greater thanthicknesses of the first and second barrier layers.

According to the embodiment, there is provided a light emitting devicepackage including a body, first and second electrode lines on the body,and a light emitting device on the body and one of the first and secondelectrode lines. The light emitting device includes a first conductivesemiconductor layer, an active layer on the first conductivesemiconductor layer, and a second conductive semiconductor layer on theactive layer. The active layer includes (T+1) barrier layers, T welllayers between the (T+1) barrier layers, and a dummy layer between Nwell layers adjacent to the second conductive semiconductor layer and Nbarrier layers adjacent to the N well layers, in which T>N≧1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a light emitting device 1 accordingto the embodiment.

FIG. 2 is a graph showing the relationship between a CRI and opticalpower.

FIG. 3 is a graph showing optical power as a function of a thickness ofthe barrier layer.

FIG. 4 is a sectional view showing an active layer according to thefirst embodiment in the light emitting device of FIG. 1.

FIG. 5 is an energy band diagram for the active layer of FIG. 4.

FIG. 6 is an energy band diagram for the active layer of FIG. 4.

FIG. 7 is a sectional view showing an active layer according to thesecond embodiment in the light emitting device of FIG. 1.

FIG. 8 is an energy band diagram for the active layer of FIG. 7.

FIG. 9 is an energy band diagram for the active layer of FIG. 7.

FIG. 10 is a graph showing optical power as a function of a wavelengthaccording to the related art and the embodiments.

FIG. 11 is a graph showing the driving voltage according to the relatedart and the embodiments.

FIG. 12 is a sectional view showing a lateral type light emitting deviceaccording to the embodiment.

FIG. 13 is a sectional view showing a flip type light emitting deviceaccording to the embodiment.

FIG. 14 is a sectional view showing a vertical type light emittingdevice according to the embodiment.

FIG. 15 is a sectional view showing a light emitting device packageaccording to the embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the description of embodiments, it will be understood that when alayer (or film), region, pattern or structure is referred to as being‘on’ or ‘under’ another layer (or film), region, pad or pattern, theterminology of ‘on’ and ‘under’ includes both the meanings of ‘directly’and ‘indirectly’. Further, the reference about ‘on’ and ‘under’ eachlayer will be made on the basis of drawings.

Hereinafter, the embodiment will be described with reference toaccompanying drawings. In the drawings, the thickness or size of eachlayer is exaggerated, omitted, or schematically illustrated forconvenience in description and clarity. In the drawings, the thicknessor size of each component is exaggerated, omitted, or schematicallyillustrated for convenience in description and clarity.

FIG. 1 is a sectional view showing a light emitting device 1 accordingto the embodiment.

Referring to FIG. 1, the light emitting device 1 according to theembodiment may include a substrate 3 and a light emitting structure 20disposed on the substrate 3.

The substrate 3 may include at least one selected from the groupconsisting of sapphire (Al₂O₃), SiC, Si, GaAs, GaN, ZnO, Si, GaP, InPand Ge.

A buffer layer 5 may be interposed between the substrate 3 and the lightemitting structure 20, but the embodiment is not limited thereto.

The buffer layer 5 may be formed to reduce a great lattice constantdifference made between the substrate 3 and the light emitting structure20. In other words, the substrate 3 may be formed thereon with thebuffer layer 5, and the buffer layer 5 may be formed thereon with thelight emitting structure 20. In this case, since the light emittingstructure 20 makes a less lattice constant difference from the bufferlayer 3, the light emitting structure 20 may be stably grown from thebuffer layer 3 without failure, so that the electrical and opticalcharacteristics can be improved.

The light emitting structure 20 may include a first conductivesemiconductor layer 7, an active layer 10, and a second conductivesemiconductor layer 9, but the embodiment is not limited thereto.

For instance, the active layer 10 may be disposed on the firstconductive semiconductor layer 7, and the second conductivesemiconductor layer 9 may be disposed on the active layer 10.

The buffer layer 5, the first conductive semiconductor layer 7, theadhesive layer 10, and the second conductive semiconductor layer 9 mayinclude a group II-VI compound semiconductor material, or a group III-Vcompound semiconductor material. For instance, the first conductivesemiconductor layer 7, the adhesive layer 10, and the second conductivesemiconductor layer 9 may include at least one selected from the groupconsisting of InAlGaN, GaN, AlGaN, InGaN, AN, InN and AlInN, but theembodiment is not limited thereto.

For instance, the first conductive semiconductor layer 7 may include anN type semiconductor layer including N type dopants, and the secondconductive semiconductor layer 9 may include a P type semiconductorlayer including P type dopants, but the embodiment is not limitedthereto. The N type dopants include Si, Ge, and Sn, and the P typedopants include Mg, Zn, Ca, Sr, and Ba, but the embodiment is notlimited thereto.

The active layer 10 may emit light having a wavelength corresponding tothe energy bandgap varied depending on a material constituting theactive layer 10 through the recombination of first carriers (e.g.,electrons), which are injected from the first conductive semiconductorlayer 7, and second carriers (e.g., holes) injected through the secondconductive semiconductor layer 9.

The active layer 27 may include one of a single quantum well structure(SQW), a multi quantum well (MQW) structure, a quantum dot structure, ora quantum wire structure, but the embodiment is not limited thereto. Theactive layer 10 may be formed by repeatedly laminating one cycle of welland barrier layers. The number of times to repeat the cycle of the welland barrier layers may vary depending on the characteristics of thelight emitting device, but the embodiment is not limited thereto.

For instance, the active layer 10 may include a cycle of InGaN/GaN, acycle of InGaN/AlGaN, or a cycle of InGaN/InGaN. The bandgap of thebarrier layer may be great than that of the well layer.

Although not shown, a third conductive semiconductor layer includingconductive dopants the same as those of the first conductivesemiconductor layer 7 may be disposed on the second conductivesemiconductor layer 9.

Although not shown, a first electrode may be disposed to contact thefirst conductive semiconductor layer 7, and a second electrode may bedisposed to contact the second conductive semiconductor layer 9 or thethird conductive semiconductor layer.

The light emitting device 1 may have one of a lateral type structure, aflip-chip type structure, and a vertical type structure.

In the lateral type structure, or the flip-chip type structure, thefirst electrode may be disposed on the first conductive semiconductorlayer 7, and the second electrode may be disposed on the secondconductive semiconductor layer 9. That is to say, in the lateral typestructure or the flip-chip type structure, the first and secondelectrodes may be disposed in the same direction.

In the vertical type structure, the first electrode may be disposed onthe first conductive semiconductor layer 7, and the second electrode maybe disposed under the second conductive semiconductor layer 9. In otherwords, the vertical type structure, the first and second electrodes maybe disposed in directions opposite to each other, and a portion of thefirst electrode may overlap with a portion of the second electrode, butthe embodiment is not limited thereto.

As shown in FIG. 2, generally, a color rendering index (CRI) is ininverse proportion to optical power.

In other words, as the wavelength of the light emitting device 1increases, the CRI may increase, and the optical power may decrease.Particularly, in the peak wavelength of less than 450 nm, as awavelength increases, the CRI increases, and the optical power mayincrease. However, from the peak wavelength of 450 nm, as the wavelengthincreases, the CRI increases, but the optical power may decrease.

Accordingly, the development on the light emitting device, which canincrease or maintain optical power with the increase of the CRI at thepeak wavelength of 450 nm or more, is strongly required.

At the wavelength of 450 nm or more, the characteristic of phosphorsdeteriorate, and the optical power lowers due to the deterioration ofthe phosphors.

In order for the light emitting device 1 to have the peak wavelength of450 nm or more, the energy bandgap of the active layer 10 needs to beadjusted. For instance, when the active layer 10 includes InGaN well/GaNbarrier layers, the energy bandgap of the active layer 10 may be variedby adjusting the content of In contained in the well layer. However, ifthe content of In increase, the quality of the active layer 10 isdegraded. Accordingly, in order to compensate for the degraded qualityof the active layer 10, the thickness of the barrier layer needs toincrease. If a plurality of barrier layers are provided, the degradedquality may be compensated by increasing the whole thickness of thebarrier layers.

FIG. 3 is a graph showing experimental data obtained by measuring theoptical power Po of the light emitting device 1 after the thickness ofthe barrier layer is sequentially changed from 65 Å to 70 Å, 80 Å and 90Å. As shown in FIG. 3, as the thickness of the barrier layer increases,the optical power Po lowers.

As the thickness of the barrier layer is reduced to 90 Å, 80 Å, and 70Å, the optical power may increase at the peak wavelength 450 nm or more.In other words, optical power may be stronger in the barrier layerhaving the thickness of 80 Å rather than the barrier layer having thethickness of 90 Å. In addition, the optical power may be stronger in thebarrier layer having the thickness of 70 Å rather than the barrier layerhaving the thickness of 80 Å. However, in the case of all of the barrierlayers having the thickness of 90 Å, the barrier layer having thethickness of 80 Å, and the barrier layer having the thickness of 70 Å,as the wavelength increases, the optical power is gradually reduced.Especially, in the case of the barrier layer having the thickness 65 Å,the optical power is rapidly reduced.

In this case, all barrier layers included in the active layer may haveequal thicknesses. For instance, the thickness of all barrier layersincluded in the active layer may be 90 Å.

As shown in FIG. 3, as the thickness of the barrier layer is reduced,the optical power is enhanced, but the driving voltage may increase. Asthe thickness of the barrier layer is reduced, the bulk resistance ofthe active layer increases, and the driving voltage increases due to theincrease of the bulk resistance. In other words, the flow of current isinterrupted due to the increase of the bulk resistance. Accordingly, inorder to allow desirable current to flow, higher driving voltage isrequired.

According to the embodiment, the light emitting device capable ofenhancing the CRI and the optical power while lowering the drivingvoltage can be realized.

FIG. 4 is a sectional view showing an active layer according to thefirst the embodiment in the light emitting device of FIG. 1.

Referring to FIG. 4, the active layer 10 may include a plurality ofbarrier layers 11 a, 11 , 11 c, and 11 d, a plurality of well layers 13a, 13 b, and 13 c, and first and second dummy layers 15 a and 15 b.

The well layers 13 a, 13 b, and 13 c may be provided between the barrierlayers 11 a, 11 b, 11 c, and 11 d. For instance, the first well layer 13a may be disposed on the first barrier layer 11 a, the second barrierlayer 11 b may be disposed on the first well layer 13 a, and the secondwell layer 13 b may be disposed on the second barrier layer 11 b. Thethird barrier layer 11 c may be disposed on the second well layer 13 b,the third well layer 13 c may be disposed on the third barrier layer 11c, and the fourth barrier layer 11 d may be disposed on the third welllayer 13 c.

The first to third well layers 13 a 13 b, and 13 c may be filled withelectrons or holes that are supplied from the related adjacent barrierlayers 11 a, 11 b, 11 c, and 11 d. The electrons and the holes may berecombined with each other to generate light.

The first and second dummy layers 15 a and 15 b may contact the thirdwell layer 13 c. In other words, the first dummy layer 15 a may contactboth of the fourth barrier layer 11 d and the third well layer 13 c, andthe second dummy layer 15 b may contact both of the third well layer 13c and the third barrier layer 11 c, but the embodiment is not limitedthereto.

The first and second dummy layers 15 a and 15 b may be included in thethird and fourth barrier layers 11 c and 11 d, respectively.Accordingly, the thickness of each of the third and fourth barrierlayers 11 c and 11 d including the first and second dummy layers 15 aand 15 b increases, so that the band bending caused by the latticeconstant difference between the third well layer 13 c and the fourthbarrier layer 11 d may be relieved, thereby increasing the opticalpower.

Accordingly, even if the composition of the compound semiconductormaterial of the third well layer 13 c greatly contributing to the lightemission is adjusted so that the man peak of 450 nm or more is formed,the quality of the active layer 10 is not affected.

In addition, the first and second dummy layers 15 a and 15 b are formedin contact with the third barrier layer 11 c and the fourth barrierlayer 11 d adjacent to the second conductive semiconductor layer 9, sothat the increase of the whole bulk resistance can be minimized and theoptical power can increase.

The active layer 10 according to the embodiment may generate lighthaving the peak wavelength of 450 nm or more, but the embodiment is notlimited thereto.

Although FIG. 4 shows that the first and second dummy layers 15 a and 15b are disposed at both sides of the third well layer 13 c, the seconddummy layer 15 b may be disposed between N well layers adjacent to thesecond conductive semiconductor layer 9 and N barrier layers adjacent tothe N well layers. In this case, N is a natural number of 1 or more(N≧1).

In this case, the total number of the well layers may be T, and thetotal number of the barrier layers may be “T+1” in which T>N. Althoughnot shown, the second dummy layer 15 b may be disposed between thesecond well layer 13 b and the third barrier layer 11 c. In other words,the second well layer 13 b may be disposed on the second barrier layer11 b, the second dummy layer 15 b may be disposed on the second welllayer 13 b, and the third barrier layer 11 c may be disposed on thesecond dummy layer 15 b. In this case, the second dummy layer 15 bincreases the thickness of the third barrier layer 11 c to relieve theband bending caused by the lattice constant difference between thesecond well layer 13 b and the third barrier layer 11 c, therebyincreasing the optical power.

For instance, the first to fourth barrier layers 11 a, 11 b, 11 c, and11 d may have thicknesses S1, S2, S3, and S4 of about 5 nm,respectively. The first and second dummy layers 15 a and 15 b may havethicknesses t1 and t2 of about 2 nm, respectively, but the embodiment isnot limited thereto.

The first and second dummy layers 15 a and 15 b may have the thicknessest1 and t2 in the range of about 2 nm to about 4 nm, but the embodimentis not limited thereto. The thickness of 2 nm or less may hardly beformed in view of the current technology, and the thickness of 4 nm ormore may lower the optical power.

FIG. 5 is an energy band diagram for the active layer of FIG. 4.Although FIG. 5 shows the energy band diagram of a conduction band forthe explanation convenience, the energy band diagram covers both of aconduction band and a valance band.

As shown in FIG. 5, the first to fourth barrier layers 11 a, 11 b, 11 c,and 11 c may have equal energy bandgap, which is greater than that ofthe first to third well layers 13 a, 13 b, and 13 c. Therefore, thefirst to third well layers 13 a, 13 b, and 13 c may be filled withelectrons or holes passing through the first to fourth barrier layers 11a, 11 b, 11 c, and 11 d.

For instance, the first to fourth barrier layers 11 a, 11 b, 11 c, and11 d may include one of GaN, AlGaN and InGaN, and the first to thirdwell layers 13 a, 13 b, and 13 c may include InGaN, but the embodimentis not limited thereto.

At least one of the first conductive semiconductor layer 7 or the secondconductive semiconductor layer 9 may have a bandgap equal to or greaterthan that of the first to fourth barrier layers 11 a, 11 b, 11 c, and 11d, but the embodiment is not limited thereto. For instance, the firstconductive semiconductor layer 7 or the second conductive semiconductorlayer 9 may include GaN or AlGaN, but the embodiment is not limitedthereto.

The first and second dummy layers 15 a and 15 b may have the energybandgap equal to that of the first to fourth barrier layers 11 a, 11 b,11 c, and 11 d, but the embodiment is not limited thereto.

The first and second dummy layers 15 a and 15 b may include a compoundsemiconductor material the same as that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 d, but the embodiment is not limitedthereto.

Therefore, the first and second dummy layers 15 a and 15 b allow thethickness S3+t1 of the third barrier layer 11 c and the thickness S4+t2of the fourth barrier layer 11 d to substantially be increase, therebypreventing band bending.

As described above, the second dummy layer 15 b may be disposed betweenthe second well layer 13 b and the third barrier layer 11 c, but theembodiment is not limited thereto.

When the second dummy layer 15 b is disposed between the second welllayer 13 b and the third barrier layer 11 c, or between the thirdbarrier layer 11 c and the third well layer 13 c, the second dummy layer15 b may allow the thickness S3+t1 of the third barrier layer 11 c to beincreased.

FIG. 6 is an energy band diagram for the active layer of FIG. 4.Although FIG. 6 shows the energy band diagram of the conduction band forthe explanation convenience, the energy band diagram covers both of theconduction band and the valance band.

As shown in FIG. 6, the first to fourth barrier layers 11 a, 11 b, 11 c,and 11 c may have equal energy bandgap, which is greater than that ofthe first to third well layers 13 a, 13 b, and 13 c.

The first and second dummy layers 15 a and 15 b may include a compoundsemiconductor material the same as that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 d, but the embodiment is not limitedthereto.

At least one of the first dummy layer or the second dummy layer 15 a and15 b may have the energy bandgap less than that of the first to fourthbarrier layers 11 a, 11 b, 11 c, and 11 c, but the embodiment is notlimited thereto. In other words, the first and second dummy layers 15 aand 15 b may have the energy bandgap greater than that of the first tothird well layers 13 a, 13 b, and 13 c, and less than that of the firstto fourth barrier layers 11 a, 11 b, 11 c, and 11 c, but the embodimentis not limited thereto. In other words, the first and second dummylayers 15 a and 15 b may have the bandgap between the bandgap of thefirst to third well layers 13 a, 13 b, and 13 c and the bandgap of thefirst to fourth barrier layers 11 a, 11 b, 11 c, and 11 c.

As first and second dummy layers 15 a and 15 b have the bandgap lessthan that of the first to fourth barrier layers 11 a, 11 b, 11 c, and 11c, electrons or holes may be more easily injected into the well layer 13c, so that the larger quantity of light can be generated to improve theinternal quantum efficiency, but the embodiment is not limited thereto.

The first and second dummy layers 15 a and 15 b allow the thicknessS3+t1 of the third barrier layer 11 c and the thickness S4+t2 of thefourth barrier layer 11 d to be increase, thereby preventing bandbending.

As described above, the second dummy layer 15 b may be disposed betweenthe second well layer 13 b and the third barrier layer 11 c, but theembodiment is not limited thereto.

When the second dummy layer 15 b is disposed between the second welllayer 13 b and the third barrier layer 11 c, or between the thirdbarrier layer 11 c and the third well layer 13 c, the second dummy layer15 b may allow the thickness S3+t1 of the third barrier layer 11 c to beincreased.

FIG. 7 is a sectional view showing an active layer according to thesecond embodiment in the light emitting device of FIG. 1.

Referring to FIG. 7, the active layer 10 may include the barrier layers11 a, 11 b, 11 c, and 11 d, the well layers 13 a, 13 b, and 13 c, andfirst to fourth dummy layers 15 a and 15 b, and 17 a and 17 b.

The well layers 13 a, 13 b, and 13 c may be disposed between the barrierlayers 11 a, 11 b, 11 c, and 11 d. For instance, the first well layer 13a may be disposed on the first barrier layer 11 a, the second barrierlayer 11 b may be disposed on the first well layer 13 a, and the secondwell layer 13 b may be disposed on the second barrier layer 11 b. Thethird barrier layer 11 c may be disposed on the second well layer 13 b,the third well layer 13 c may be disposed on the third barrier layer 11c, and the fourth barrier layer 11 d may be disposed on the third welllayer 13 c.

The first to third well layers 13 a 13 b, and 13 c may be filled withelectrons or holes supplied from the related adjacent barrier layers 11a, 11 b, 11 c, and 11 d. The electrons and the holes may be recombinedwith each other to generate light.

The first and second dummy layers 15 a and 15 b may contact the thirdwell layer 13 c. In other words, the first dummy layer 15 a may contactboth of the fourth barrier layer 11 d and the third well layer 13 c, andthe second dummy layer 15 b may contact both of the third well layer 13c and the third barrier layer 11 c, but the embodiment is not limitedthereto.

The first and second dummy layers 15 a and 15 b increase the thicknessesof the third barrier layer 11 c and the fourth barrier layer 11 d,respectively, to relieve the band bending caused by the lattice constantdifference between the third well layer 13 c and the fourth barrierlayer 11 d, thereby increasing the optical power.

Although not shown, the first dummy layer 15 a may be interposed betweenthe second well layer 13 b and the third barrier layer 11 c. In otherword, the second well layer 13 b may be disposed on the second barrierlayer 11 c, the second dummy layer 15 b may be disposed on the secondwell layer 13 b, and the third barrier layer 11 c may be disposed on thesecond dummy layer 15 b. In this case, the second dummy layer 15 bincreases the thickness of the third barrier layer 11 c to relieve theband bending caused by the lattice constant difference between thesecond well layer 13 b and the third barrier layer 11 c, therebyincreasing the optical power.

The third and fourth dummy layers 17 a and 17 b may contact the firstwell layer 13 a. In other words, the third dummy layer 17 a may contactboth of the first barrier layer 11 a and the first well layer 13 a, andthe fourth dummy layer 17 b may contact both of the first well layer 13a and the second barrier layer 11 b, but the embodiment is not limitedthereto.

The third and fourth dummy layers 17 a and 17 b increase the thicknessesof the first barrier layer 11 a and the second barrier layer 11 b,respectively, to relieve the band bending caused by the lattice constantdifference between the first well layer 13 a and the second barrierlayer 11 b, thereby increasing the optical power.

The third and fourth dummy layers 17 a and 17 b may include a compoundsemiconductor material the same as that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 d, but the embodiment is not limitedthereto.

Although FIG. 7 shows that the third and fourth dummy layers 17 a and 17b are disposed at both sides of the first well layer 13 a, the fourthdummy layer 17 b may be disposed between M well layers adjacent to thefirst conductive semiconductor layer 7 and M barrier layers adjacent tothe M well layers. In this case, M is a natural number of 1 or more(M≧1).

In addition, although FIG. 7 shows that the first and second dummylayers 15 a and 15 b are disposed at both sides of the third well layer13 c, the second dummy layer 15 b may be disposed between N well layersadjacent to the second conductive semiconductor layer 9 and N barrierlayers adjacent to the N well layers. In this case, N is a naturalnumber of 1 or more (N≧1).

In this case, the N may be equal to or different from the M. Forinstance, the N may be greater than the M, but the embodiment is notlimited thereto.

In this case, the total number of the well layers is T, and the totalnumber of the barrier layers may be “T+1” in which T>N≧M.

Although not shown, the fourth dummy layer 17 b may be interposedbetween the second barrier layer 11 b and the second well layer 13 b. Inother words, the fourth dummy layer 17 b may be disposed on the secondbarrier layer 11 b, and the second well layer 13 b may be disposed onthe fourth dummy layer 17 b. In this case, the fourth dummy layer 17 bincreases the thickness of the second barrier layer 11 b to relieve theband bending caused by the lattice constant difference between thesecond well layer 13 b and the second barrier layer 11 b, therebyincreasing the optical power.

The first and second dummy layers 15 a and 15 b may have the thicknessesdifferent from those of the third and fourth dummy layers 17 a and 17 b.For instance, the first to fourth barrier layers 11 a, 11 b, 11 c, and11 d may have the thicknesses S1, S2, S3, and S4 of about 5 nm, and thefirst and second dummy layers 15 a and 15 b may have the thicknesses t1and t2 of about 2 nm. The third and fourth dummy layers 17 a and 17 bmay have the thicknesses u1 and u2 of 1 nm, but the embodiment is notlimited thereto.

For instance, the first and second dummy layers 15 a and 15 b may havethe thicknesses t1 and t2 in the range of about 2 nm to about 4 nm, andthe third and fourth dummy layers 17 a and 17 b may have the thicknessesu1 and u2 in the range of about 1 nm to about 2 nm, but the embodimentis not limited thereto.

FIG. 8 is an energy band diagram for the active layer of FIG. 7.Although FIG. 8 shows the energy band diagram of a conduction band forthe explanation convenience, the energy band diagram covers both of theconduction band and the valance band.

The following description will be made while focusing on the third andfourth dummy layers because the energy band diagram of FIG. 8 issubstantially similar to that of FIG. 5 except for the third and fourthdummy layers.

As shown in FIG. 8, the first to fourth barrier layers 11 a, 11 b, 11 c,and 11 c may have equal energy bandgap, which is greater than that ofthe first to third well layers 13 a, 13 b, and 13 c.

The first and second dummy layers 15 a and 15 b may have the energybandgap equal to that of the first to fourth barrier layers 11 a, 11 b,11 c, and 11 d, but the embodiment is not limited thereto.

The first and second dummy layers 15 a and 15 b may include a compoundsemiconductor material the same as that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 d, but the embodiment is not limitedthereto.

Therefore, the first and second dummy layers 15 a and 15 b substantiallyincrease the thickness S3+t1 of the third barrier layer 11 c and thethickness S4+t2 of the fourth barrier layer 11 d to prevent bandbending.

In addition, the third and fourth dummy layers 17 a and 17 b may havethe energy bandgap equal to that of the first to fourth barrier layers11 a, 11 b, 11 c, and 11 d, but the embodiment is not limited thereto.

The third and fourth dummy layers 17 a and 17 b may include a compoundsemiconductor material the same as that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 d, but the embodiment is not limitedthereto.

Therefore, the third and fourth dummy layers 17 a and 17 b allow thethickness S3+u1 of the first barrier layer 11 a and the thickness S2+u2of the second barrier layer 11 b to be increase, thereby preventing bandbending.

FIG. 9 is an energy band diagram for the active layer of FIG. 7.Although FIG. 9 shows the energy band diagram of the conduction band forthe explanation convenience, the energy band diagram covers both of theconduction band and the valance band.

The following description will be made while focusing on the third andfourth dummy layers because the energy band diagram of FIG. 8 issubstantially similar to that of FIG. 6 except for the third and fourthdummy layers.

As shown in FIG. 9, the third and fourth dummy layers 17 a and 17 b mayhave the energy bandgap less than that of the first to fourth barrierlayers 11 a, 11 b, 11 c, and 11 c, but the embodiment is not limitedthereto. In other words, the third and fourth dummy layers 17 a and 17 bmay have the energy bandgap greater than that of the first to third welllayers 13 a, 13 b, and 13 c, and less than that of the first to fourthbarrier layers 11 a, 11 b, 11 c, and 11 c, but the embodiment is notlimited thereto. In other words, the third and fourth dummy layers 17 aand 17 b may have the bandgap between the bandgap of the first to thirdwell layers 13 a, 13 b, and 13 c and the bandgap of the first to fourthbarrier layers 11 a, 11 b, 11 c, and 11 c.

The third and fourth dummy layers 17 a and 17 b allow the thicknessS3+u1 of the first barrier layer 11 a and the thickness S2+u2 of thesecond barrier layer 11 b to be increased, thereby preventing bandbending.

As described above, the fourth dummy layer 17 b may be interposedbetween the second barrier layer 11 b and the second well layer 13 b,but the embodiment is not limited thereto.

FIG. 10 is a graph showing optical power as a function of a wavelengthaccording to the related art and the embodiments.

As shown in FIG. 10, according to the related art, optical power ismainly distributed at the peak wavelength of 450 nm or less. On thecontrary, according to the first and second embodiments, the opticalpower is mainly distributed at the peak wavelength of 450 nm or more,and the optical power increases more than that of the related art.

In this case, the first embodiment may relate to the light emittingdevice including the active layer according to the first embodiment ofFIG. 4, and relate to “MQB 5577 ” of FIG. 10. The second embodiment mayrelate to the light emitting device including the active layer accordingto the second embodiment of FIG. 7, and relate to “MQB 6677” of FIG. 10.

FIG. 11 is a graph showing the driving voltage according to the relatedart and the embodiments.

The driving voltage according to the related art may be 3.028 V, thedriving voltage according to the first embodiment may be 3.029 V, andthe driving voltage of the second embodiment may be 3.008 V.

In particular, the driving voltage of the second embodiment is lowerthan that of the related art even though the thickness of the barrierlayer of the second embodiment is thicker than that of the barrier layeraccording to the related art.

As recognized from FIGS. 10 and 11, the light emitting device accordingto the embodiment represents an improved CRI and improved optical powerat the peak wavelength of 450 nm or more, and represents the lowerdriving voltage.

As described above, although description has been made in that the dummylayer is distinguished from the barrier layer, the dummy layer and thebarrier layer may be regarded as one layer. In other words, the firstdummy layer 15 a is included in the fourth barrier layer 11 d so thatthe thickness of the fourth barrier layer 11 d may be defined as S4+t2,and the second dummy layer 15 b is included in the third barrier layer11 d, so that the thickness of the third barrier layer 11 c may bedefined as S3+t1. The third dummy layer 17 a is included in the firstbarrier layer 11 a so that the thickness of the first barrier layer 11 amay be defined as S1+u1, and the fourth dummy layer 17 b is included inthe second barrier layer 11 b, so that the thickness of the secondbarrier layer 11 b may be defined as S2+u2.

FIGS. 12 to 14 are sectional views showing a product to which the lightemitting device of FIG. 1 is actually applied.

FIG. 12 is a sectional view showing a lateral type light emitting deviceaccording to the embodiment.

Referring to FIG. 12, the lateral type light emitting device accordingto the embodiment may include the substrate 3, the buffer layer 5, thelight emitting structure 20, a conductive layer 32, and first and secondelectrodes 34 and 36.

Since the substrate 3, the buffer layer 5, and the light emittingstructure 20 have been described in detail, the details thereof will beomitted in order to redundancy.

The conductive layer 32 may be disposed on the light emitting structure20, in detail, on the second conductive semiconductor layer 9. If athird conductive semiconductor layer including conductive dopants thesame as those of the first conductive semiconductor layer 7 is disposedon the second conductive semiconductor layer 9, the conductive layer 32may be disposed on the third conductive semiconductor layer.

The conductive layer 32 spreads current or makes ohmic contact with thelight emitting structure 20, so that the current can more easily flowthrough the light emitting structure 20, but the embodiment is notlimited thereto.

The conductive layer 32 may include a transparent conductive materialallowing light to pass therethrough. The transparent conductive materialmay include at least one selected from the group consisting of ITO, IZO(In—ZnO), GZO (Ga—ZnO), AZO (Al—ZnO), AGZO (Al—Ga ZnO), IGZO (In—GaZnO), IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au and Ni/IrOx/Au/ITO, but theembodiment is not limited thereto.

The first electrode 34 may be electrically connected to the firstconductive semiconductor layer 7, and the second electrode 36 may beelectrically connected to the conductive layer 32, but the embodiment isnot limited thereto.

The first and second electrodes 34 and 36 may include one selected fromthe group consisting of, for example, Al, Ti, Cr, Ni, Pt, Au, W, Cu andMo or the stack structure thereof, but the embodiment is not limitedthereto.

Although not shown, a current blocking layer may be disposed to preventcurrent from being concentrated on the lower portion of each of thefirst and second electrodes 34 and 36.

FIG. 13 is a sectional view showing a flip type light emitting deviceaccording to the embodiment.

FIG. 13 shows the structure similar to that of FIG. 12 except for thereflective layer.

Referring to FIG. 13, the flip type light emitting device according tothe embodiment may include the substrate 3, a buffer layer 5, the lightemitting structure 20, a reflective layer 42, and first and secondelectrodes 44 and 46.

The buffer layer 5 may be disposed under the substrate 3, and the lightemitting structure 20 may be disposed under the buffer layer 5. Thereflective layer 42 may be disposed under the light emitting structure20, the first electrode 44 may be disposed under the first conductivesemiconductor layer 7, and the second electrode 44 may be disposed underthe second conductive semiconductor layer, but the embodiment is notlimited thereto.

Since the substrate 3, the buffer layer 5, and the light emittingstructure 20 have been described in detail, the detail thereof will beomitted in order to avoid redundancy.

The reflective layer 42 may be disposed on the light emitting structure20, in detail, on the second conductive semiconductor layer 9. When athird conductive semiconductor layer including conductive dopants thesame as those of the first conductive semiconductor layer 7 is disposedunder the second conductive semiconductor layer 9, the reflective layer42 may be disposed under the third conductive semiconductor layer.

The reflective layer 42 reflects upward light, which is generated fromthe active layer 10 and directed downward, so that the light emissionefficiency can be improved, but the embodiment is not limited thereto.

The reflective layer 42 includes a reflective material representing asuperior reflection characteristic. For example, the reflective layer 42may include one selected from the group consisting of, for example, Ag,Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf, or the stack structurethereof, but the embodiment is not limited thereto.

If the reflective layer 42 represents an inferior ohmic contactcharacteristic with respect to the second conductive semiconductor layer9, a conductive layer (not shown) may be disposed between the secondconductive semiconductor layer 9 and the reflective layer 42, but theembodiment is not limited thereto. The conductive layer may include atransparent material representing a superior ohmic contactcharacteristic with respect to the second conductive semiconductor layer9. For example, the conductive layer may include at least one selectedfrom the group consisting of ITO, IZO (In—ZnO), GZO (Ga—ZnO), AZO(Al—ZnO), AGZO (Al—Ga ZnO), IGZO (In—Ga ZnO), IrOx, RuOx, RuOx/ITO,Ni/IrOx/Au and Ni/IrOx/Au/ITO, but the embodiment is not limitedthereto.

FIG. 14 is a sectional view showing a vertical type light emittingdevice according to the embodiment.

In the following description referring to FIG. 14, the details ofcomponents having the same functions as those of components shown inFIG. 12 will be omitted.

Referring to FIG. 14, the vertical type light emitting device accordingto the embodiment may include a support substrate 61, an adhesion layer59, an electrode layer 57, an ohmic contact layer 55, a current blockinglayer 53, a channel layer 51, a protective layer 63, and an electrode65.

The support substrate 61 may not only support a plurality of layersformed thereon, but serve as an electrode.

The support substrate 61 may include at least one of titanium (Ti),chrome (Cr), nickel (Ni), aluminum (Al), platinum (Pt), gold (Au),tungsten (W), copper (Cu), molybdenum (Mo) and copper-tungsten (Cu—W).

The adhesion layer 59 serves as a bonding layer, and is interposedbetween the electrode layer 57 and the support substrate 61. Theadhesion layer 59 may serve as a medium to enhance the adhesive strengthbetween the electrode layer 57 and the support substrate 61.

For instance, the adhesion layer 59 may include at least one selectedfrom the group consisting of Ti, Au, Sn, Ni, Nb, Cr, Ga, In, Bi, Cu, Agand Ta.

The electrode layer 57 serves as an electrode to supply power to theactive layer 10, and reflects upward light, which is generated from theactive layer 10 and directed downward. The electrode layer 57 may benamed a reflective layer.

If the electrode layer 57 represents a superior ohmic contactcharacteristic with respect to the second conductive semiconductor layer9, the ohmic contact layer 55 may be omitted. In this case, theelectrode layer 57 may have an electrode function, a reflectivefunction, and an ohmic contact function.

The electrode layer 57 may include one selected from the groupconsisting of, for example, Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au,and Hf, or the stack structure thereof, but the embodiment is notlimited thereto.

The channel layer 51 may be formed along the peripheral region betweenthe electrode layer 57 and the second conductive semiconductor layer 9.The channel layer 51 may be surrounded by both of the electrode layer 57and the second conductive semiconductor layer 9 if the ohmic contactlayer 55 is omitted.

The channel layer 51 may prevent the electrical short from occurringbetween the lateral side of the electrode layer 57 and the lateral sideof the light emitting structure 20 due to external foreign matters.

The channel layer 51 may include an insulating material, for example, atleast one of selected from the group consisting of SiO2, SiOx, SiOxNy,Si3N4, and Al2O3.

In order to prevent current from being concentrated, the currentblocking layer 53 may be interposed between the second conductivesemiconductor layer 9 and the electrode layer 57.

The current blocking layer 53 may overlap with a portion of theelectrode 65.

In the vertical type light emitting device, since the electrode layer 57has the shape of a plate, and the electrode 65 is formed in the shape ofa pattern only at a portion of the light emitting structure 20, if poweris applied to the electrode 65 and the electrode layer 57, currentconcentratedly flows in a vertical direction of the electrode 65.Therefore, the current blocking layer 53 is disposed at a positionvertically overlapping with the electrode 65, so that the currentvertically flowing through the electrode 65 is dispersed to theperipheral portion of the current blocking layer 53.

The current blocking layer 53 may have electrical conductivity less thanthat of the electrode layer 57, have an electrical insulating propertygreater than that of the electrode layer 57, or have a material to makeschottky contact with the light emitting structure 20. The currentblocking layer 53 may include, for example, at least one selected fromthe group consisting of ITO, IZO, IZTO, IAZO, IGZO, IGTO, AZO, ATO, ZnO,SiO₂, SiO_(x), SiO_(x)N_(y), Si₃N₄, Al₂O₃, TiOx, Ti, Al and Cr. In thiscase, the SiO₂, SiO_(x), SiO_(x)N_(y), Si₃N₄, and Al₂O₃ may beinsulating materials.

The protective layer 63 may be disposed around the lateral side of thelight emitting structure 20. A portion of the protective layer 63contacts the top surface of the channel layer 51, and another portion ofthe protective layer 63 may be disposed at a peripheral region of thetop surface of the first conductive semiconductor layer 7.

The protective layer 63 may prevent electrical short from occurringbetween the light emitting structure 20 and the support substrate 61.For instance, the protective layer 63 may include an insulating materialincluding one selected from the group consisting of SiO₂, SiO_(x),SiO_(x)N_(y), Si₃N₄, TiO₂ and Al₂O₃, but the embodiment is not limitedthereto.

The protective layer 63 may include a material the same as that of thechannel layer 51, but the embodiment is not limited thereto.

The first conductive semiconductor layer 7 may be provided at a topsurface thereof with a light extraction structure to effectively extractlight. The light extraction structure may have a concave-convexstructure or a roughness structure. The concave-convex structure may beuniformly or randomly formed.

The electrode 65 may be disposed on the light extraction structure.

For example, the electrode 65 may include one selected from the groupconsisting of Al, Ti, Cr, Ni, Pt, Au, W, Cu and Mo, or the stackstructure thereof, but the embodiment is not limited thereto.

FIG. 15 is a sectional view showing a light emitting device packageaccording to the embodiment.

Referring to FIG. 15, the light emitting device package according to theembodiment includes a body 101, first and second electrode lines 103 and105 installed in the body 101, a light emitting device 107 to receivepower from the first and second electrode lines 103 and 105, and amolding member 113 surrounding the light emitting device 107.

The body 101 may include a silicon material, a synthetic resin material,or a metallic material, and may have the inclined surfaces formed aroundthe light emitting device 107.

The first and second electrode lines 103 and 105 are electricallyinsulated from each other to supply power to the light emitting device107.

In addition, the first and second electrode lines 103 and 105 reflectlight generated from the light emitting device 107 to increase the lightefficiency and discharge heat generated from the light emitting device107 to the outside.

The light emitting device 107 may be installed on one of the firstelectrode line 103, the second electrode line 105, and the body 101. Thelight emitting device 107 may be electrically connected to the first andsecond electrode lines 103 and 105 through a wire scheme or a diebonding scheme, but the embodiment is not limited thereto. For example,one side of the light emitting device 107, for example, the bottomsurface of the light emitting device 107 may be electrically connectedto the top surface of the first electrode line 103, and an opposite sideof the light emitting device 107 may be electrically connected to thesecond electrode line 105 through the wire 109.

The light emitting device 107 according to the embodiment may be one ofthe lateral type light emitting device, the flip-chip light emittingdevice, and the vertical type light emitting device described above, butthe embodiment is not limited thereto.

The molding member 113 may surround the light emitting device 107 toprotect the light emitting device 107. In addition, the molding member113 includes phosphors so that the wavelength of the light emitted fromthe light emitting device 107 may be converted.

The light emitting device package according to the embodiment may have achip on board (COB), the body 101 may have a flat top surface, and aplurality of light emitting devices 107 may be installed in the body101.

According to the embodiment, dummy layers having bandgap similar tothose of barrier layers are formed in adjacent to the barrier layers, sothat the CRI and the optical power can be improved, and the voltage canlower at the peak wavelength of 450 nm or more.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device comprising: a firstconductive semiconductor layer; an active layer on the first conductivesemiconductor layer; and a second conductive semiconductor layer on theactive layer, wherein the active layer comprises: (T+1) barrier layers;T well layers between the (T+1) barrier layers; and a first dummy layerbetween N well layers adjacent to the second conductive semiconductorlayer and N barrier layers adjacent to the N well layers, in whichT>N≧1.
 2. The light emitting device of claim 1, wherein the active layerfurther comprises a second dummy layer between M well layers adjacent tothe first conductive semiconductor layer and M barrier layers adjacentto the M well layers, in which N≧M≧1.
 3. The light emitting device ofclaim 2, wherein the first dummy layer is disposed on one of a topsurface and a bottom surface of the barrier layers.
 4. The lightemitting device of claim 2, wherein the second dummy layer is disposedon one of a top surface and a bottom surface of the barrier layers. 5.The light emitting device of claim 2, wherein the active layer furthercomprises a third dummy layer between a first barrier layer contactingthe second conductive semiconductor layer and a first well layercontacting the first barrier layer.
 6. The light emitting device ofclaim 5, wherein each of the first to third dummy layers has a thicknessin a range of about 2 nm to about 4 nm.
 7. The light emitting device ofclaim 5, wherein the first dummy layer is disposed on one of a topsurface and a bottom surface of a second barrier layer contacting thefirst well layer.
 8. The light emitting device of claim 5, wherein theactive layer further comprises a fourth dummy layer between a thirdbarrier layer contacting the first conductive semiconductor layer and asecond well layer contacting the third barrier layer.
 9. The lightemitting device of claim 8, wherein each of the second and fourth dummylayers has a thickness in a range of about 1 nm to about 2 nm.
 10. Thelight emitting device of claim 8, wherein the second dummy layer isdisposed on one of a top surface and a bottom surface of a fourthbarrier layer contacting the second well layer.
 11. The light emittingdevice of claim 8, wherein at least one of the first to fourth dummylayers has a bandgap equal to a bandgap of the first barrier layer. 12.The light emitting device of claim 8, wherein at least one of the firstto fourth dummy layers has a bandgap between a bandgap of the first welllayer and a bandgap of the first barrier layer.
 13. The light emittingdevice of claim 8, wherein at least one of the first to fourth dummylayers includes the same compound semiconductor material as a compoundsemiconductor material of the first barrier layer.
 14. The lightemitting device of claim 1, wherein the (T+1) barrier layers have equalthicknesses.
 15. The light emitting device of claim 1, wherein theactive layer generates a light having a peak wavelength of 450 nm ormore.
 16. A light emitting device comprising: a substrate; a firstconductive semiconductor layer on the substrate; an active layer on thefirst conductive semiconductor layer; and a second conductivesemiconductor layer on the active layer, wherein the active layercomprises: first to fourth barrier layers; and first to third welllayers between the first to fourth barrier layers, and wherein the firstbarrier layer contacts the first conductive semiconductor layer, thefourth barrier layer contacts the second conductive semiconductor layer,and the third and fourth barrier layers have thicknesses greater thanthicknesses of the first and second barrier layers, respectively. 17.The light emitting device of claim 16, wherein the thickness of each ofthe first and second barrier layers is about 5 nm, and the thickness ofeach of the third and fourth barrier layers is about 7 nm.
 18. The lightemitting device of claim 16, wherein the thickness of each of the firstand second barrier layers is about 6 nm, and the thickness of each ofthe third and fourth barrier layers is about 7 nm.
 19. The lightemitting device of claim 16, wherein the first conductive semiconductorlayer is an N type semiconductor layer, and the second conductivesemiconductor layer is a P type semiconductor layer.
 20. A lightemitting device package comprising: a body; first and second electrodelines on the body; and a light emitting device on the body or one of thefirst and second electrode lines, wherein the light emitting devicecomprises: a first conductive semiconductor layer; an active layer onthe first conductive semiconductor layer; and a second conductivesemiconductor layer on the active layer, and wherein the active layercomprises: (T+1) barrier layers; T well layers between the (T+1) barrierlayers; and a first dummy layer between N well layers adjacent to thesecond conductive semiconductor layer and N barrier layers adjacent tothe N well layers, in which T>N≧1.